Microsoft has agreed to acquire business software company Yammer for more than $1 billion, a person familiar with the matter told The Wall Street Journal.

The report did not indicate when the acquisition is expected to be announced or completed.

Yammer representatives declined to comment. CNET has also contacted Microsoft for comment and will update this report when we learn more.

San Francisco-based Yammer is sort of like Facebook for companies: employees can post, share, and discuss items. It's become an integral tool for many startups, but it's also big among larger businesses. More than 80 percent of Fortune 500 companies use Yammer. If Microsoft buys Yammer, the move could help the tech titan modernize with social-enterprise tools.

Rumors of a Microsoft buyout began to surface yesterday when Business Insider reported that several people near Yammer's San Francisco headquarters were overheard discussing the acquisition. In addition to a woman tweeting that she had also overheard similar talk at a coffee shop near Yammer's offices, a source "inside Yammer" told Business Insider that a deal was near.